The Western Roman Empire refers to western half of the Roman Empire.

Administrative division of the sprawling Empire into West and East with co-emperors for each begins under Diocletian in 285 and is periodically abolished and recreated for the next two centuries until final abolishment by Zeno in 480.

By this time there is little effective control left in the Western Empire.A Western Roman Empire exists intermittently in several periods between the 3rd and 5th centuries, after Diocletian's Tetrarchy and the reunifications associated with Constantine the Great and Julian the Apostate (324–363).

Theodosius I divides the Empire upon his death (in 395) between his two sons.

Eighty-five years later, Zeno recognizes the reality of the Western Empire's reduced domain (Imperial control had been lost over even the Italian Peninsula) after the death of Western Emperor Julius Nepos and rules as sole emperor.The rise of Odoacer of the Foederati to rule over Italy in 476 was popularized by eighteenth century historian Edward Gibbon as a demarcating event for the end of the Western Empire and is still used today to mark the transition from Antiquity to the Middle Ages.The ongoing struggle between the rising Papacy and the retreating empire leads the Pope to unilaterally declare the Frankish King Charlemagne to be the successor of the Western Emperors in 800.

This new imperial line will evolve in time into the Holy Roman Empire, but is in no meaningful sense an extension of Roman traditions or institutions.

After 924 it is also a primarily Germanic empire that contains little of the former territory of the Western Roman Empire.